1. Field of the Invention
The invention relates in general to duplex microwave radio communication system for transmission of analog and digital data between mobile transmitter and receiver stations along the side of prescribed routes wherein fixed transmitter receiver stations are located and wherein the transmitter and receiver stations are effective to transmit and receive information in both directions and in which the stations for one route are connected to a central transmitter-receiver station and further the invention relates to a method for stabilizing the microwave oscillator in the transmitter branch of a transmitter-receiver station.
2. Description of the Prior Art
Radio systems of the duplex microwave radio type are important in railroad traffic. For the economic utilization of existing railroad networks which have high density of trains travelling at high speed requires that more efficient and increasing data and signal exchange exist between the trains and the stationary fixed equipment.
The publication "Electric Railways" 44 (1973) Volume 4, at pages 83 through 92 disclose information exchange utilizing a so-called line conductor system. In these systems, inductive wire loops are arranged in the track area for a line conductor system and the wire loops serve as transmitter-receiver antenna for the stationary stations. The transmission of information between the mobile transmitter-receiver stations on the vehicle and these stationary stations utilizes a frequency shift in the frequency range of about 50 kHz and the maximum transmission rate is limited to approximately 1200 bauds. In addition to having limited rate of information flow, the line conductor system has the great disadvantage in that the wire loops particularly during railroad track construction work can be easily damaged which degradates the system.
The disadvantage of mechanical damage in such radio systems can be prevented if the inductive loops for the transmission are abandoned and the stations in contact with one another exchange information by way of radio. Such systems, for example, are disclosed in the publication "ETR" (Railway Technical Review), Volume 10, October 1971 at pages 402 through 411.
In an earlier patent application of the assignee, a radio station is improved utilizing these known systems and it was suggested that the route segments between consecutive stations representing main stations can be subdivided by intermediate stations with the main stations and the intermediate stations which are closest together in distance are combined into transmission segments and the intermediate stations together with the corresponding main stations are utilized for signal and communication exchange with the mobile stations.